Nanocrystalline CuMO2 (M = BIII, AlIII, GaIII, InIII, ScIII, CrIII) metal oxides are an attractive family of wide band gap p-type semiconductors with high demand for applications in organic photovoltaics, perovskite solar cells, and dye-sensitized solar cells. In these devices, CuMO2 materials act as hole transport layers whereby they facilitate the transfer/transport of electron vacancies (i.e. holes) from the photoactive layer to the external circuit. Currently, NiO is the most well studied p-type metal oxide within this field; however, serious challenges exist with regard to its low hole mobility and lack of transparency in the visible region.
The storage of electrochemical energy in molecular species is a critical challenge to many energy conversion strategies; from dye-sensitized solar cells to photo/electrocatalytic water splitting to redox flow batteries. Arguably, the best method to store electrochemical energy within molecules is by the formation of chemical bonds coupled to multi-electron oxidation/reduction reactions. For example, water splitting results in the 2e– reduction of 2H+ to H2 to form an H-H bond and the 4e– oxidation of 2H2O to O2 to form an O=O double bond.